Coils having a preselected resistance value are used for various applications, such as current coils for injection valves. One problem in manufacturing these types of coils with conventional automatic winding machines, is that the resistance value of the wire typically does not remain constant along the entire length of the coil. For example, there may be variations in the alloy of the base material, or various conditions during the process of drawing the wire, that may cause the resistance of the wire to vary. The resistance of a wound coil is also influenced by the ambient conditions during the process of winding the coil, such as the room temperature.
It is an object of the present invention, therefore, to overcome the problems of known methods and apparatus for manufacturing coils and to provide coils having substantially predetermined electrical resistance characteristics.